1. Field of the invention
The present invention concerns locating addresses on articles to be despatched so that the addresses can be read automatically so that the articles can be sorted automatically. It applies to articles of all kinds and in particular a wide range of mail items, especially magazines, large envelopes, packets and the like.
2. Description of the prior art
The increasingly automated sorting of mail items is made possible by the use of image processing and character recognition techniques. These techniques process a digitized image of the articles to be sorted. Whatever character recognition method is used, one of the preliminary functions to be implemented before reading the mailing address is to locate the address within all of the information constituting the digitized image of each article.
Known methods of locating addresses on articles are essentially of two types.
One type uses the optical properties of certain mail items. The methods in most widespread use are based on the difference in optical reflection due to the presence of an address window in an envelope. Other methods of this kind detect the excess thickness due to an address label stuck onto the article or the edges of an addressing window on the article. The additional thickness is detected by means of coherent light.
The second type methods operate directly on the digitized images of the articles to be sorted. They are based on recognizing the shape of each article and use characteristics defining the position of the addressing area on each article.
Locating the addressing area by a method of either of these two types enables its content to be scanned and thus enables the automatic reading of addresses for automatic sorting of articles. The methods of the first type give good results but they are generally adopted only for mail items comprising window envelopes. The second type methods cover a wider range of mail items, but sometimes yield incorrect results. They lead to errors if the addresses do not comply with position specifications as defined, for example, by mailing standards. This is the case in particular if the address labels are applied by hand and positioned incorrectly or in the case of address labels which, although initially stuck on in the correct position, have come unstuck and have moved on the surface of the article, inside a plastics wrap containing them. Under such conditions the known methods cannot distinguish the address, to enable it to be scanned, from any advertising or other information on the wrap and/or the article and reproduced in the digitized image of the article.
An object of the present invention is to avoid the drawbacks of these known methods by enabling the address to be located within the digitized image of a broad spectrum of articles, virtually free of errors and irrespective of the position and the orientation of the address on the article and therefore in the image, for subsequent automatic processing of such articles.